/******* 服务器程序  (server.c) ************/
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <netdb.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <sys/types.h>
#include <arpa/inet.h>

int main(int argc, char *argv[])
{
    int sockfd,new_fd;
    struct sockaddr_in server_addr;
    struct sockaddr_in client_addr;
    int sin_size,portnumber;
    char hello[]="Hello! Are You Fine?\n";

    if(argc!=2)
    {
        fprintf(stderr,"Usage:%s portnumber\a\n",argv[0]);
        exit(1);
    }

    if((portnumber=atoi(argv[1]))<0)
    {
        fprintf(stderr,"Usage:%s portnumber\a\n",argv[0]);
        exit(1);
    }

    /* 服务器端开始建立socket描述符 */
    if((sockfd=socket(AF_INET,SOCK_STREAM,0))==-1)  
    {
        fprintf(stderr,"Socket error:%s\n\a",strerror(errno));
        exit(1);
    }

    /* 服务器端填充 sockaddr结构  */ 
    bzero(&server_addr,sizeof(struct sockaddr_in));
    server_addr.sin_family=AF_INET;
    server_addr.sin_addr.s_addr=htonl(INADDR_ANY);
    server_addr.sin_port=htons(portnumber);

    /* 捆绑sockfd描述符  */ 
    if(bind(sockfd,(struct sockaddr *)(&server_addr),sizeof(struct sockaddr))==-1)
    {
        fprintf(stderr,"Bind error:%s\n\a",strerror(errno));
        exit(1);
    }

    /* 监听sockfd描述符  */
    if(listen(sockfd,5)==-1)
    {
        fprintf(stderr,"Listen error:%s\n\a",strerror(errno));
        exit(1);
    }

    while(1)
    {
        /* 服务器阻塞,直到客户程序建立连接  */
        sin_size=sizeof(struct sockaddr_in);
        if((new_fd=accept(sockfd,(struct sockaddr *)(&client_addr),&sin_size))==-1)
        {
            fprintf(stderr,"Accept error:%s\n\a",strerror(errno));
            exit(1);
        }

        fprintf(stderr,"Server get connection from %s\n",
                inet_ntoa(client_addr.sin_addr));
        if(write(new_fd,hello,strlen(hello))==-1)
        {
            fprintf(stderr,"Write Error:%s\n",strerror(errno));
            exit(1);
        }
        /* 这个通讯已经结束     */
        close(new_fd);
        /* 循环下一个     */  
    }
    close(sockfd);
    exit(0);
}

